Category Archives: titan

astronomy, cassini, cassini mission, saturn, titan

Sailing Over Titan’s Seas in Summer

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Cassini Captures Cloud Movement Over Ligeia Mare

An animated gif of clouds moving across Titan's northern Ligeia Mare (sea). Watch the clouds over the dark area lower center/right. Credit: NASA/JPL-Caltech/SSI
An animated gif of clouds moving across Titan’s northern Ligeia Mare (sea). Watch the clouds over the dark area lower center/right. Credit: NASA/JPL-Caltech/SSI

If you’ve ever been aboard a sailing ship, you probably know the sensation of the craft cutting through the ocean, wind at your back and a breeze in your face. It’s probably the same sensation you get when you go hang-gliding, or water (or snow) skiing.

It turns out, if you lived on Saturn’s icy but intriguing moon  Titan, you could experience the same sensations (provided you could survive the atmosphere and cold temperatures). Of course, your ship would need to be able to withstand the frigid methane sea, and the cold, largely nitrogen (with small amounts of methane and hydrogen) atmosphere.

The clouds would be made of methane, possibly some ammonia, and other hydrocarbons. Feeling the breeze on your face would require you to withstand an atmospheric pressure about 1.5 times that of Earth’s sea level, and near-surface temperatures of about 94 Kelvin (-297 F, or -179 C). Not impossible, but right now, pretty improbable. That’s why we have the Cassini-Solstice Mission — to give us a spacecraft-eye view of what it might look like from above.

So, what would a cloudy, breezy sea day on Titan be like? Cassini scientists just released an animation of clouds blowing across the surface of the northern Titan sea called Ligeia Mare. In the sequence (which you can see here), the clouds blow just over the hydrocarbon-rich sea at speeds of around 7 to 10 miles per hour (3-4.5 meters/second). These images were taken a few weeks ago (late July), and the formation of the clouds and their actions may be harbingers of summer on Titan.

Titan does indeed have seasons during its 30-Earth-year-long year. Each of those seasons lasts about 7 Earth years, giving plenty of time for seasonal change to occur. When Cassini first arrived at Saturn and began studying this moon, its northern pole was pointed away from the Sun, which put it in high winter. At that time, the north polar region was shrouded with a hazy hood. There was a lot of cloud activity in the southern hemisphere (during its summer, when things were a bit warmer (relatively)).

As equinox approached, when both northern and southern hemisphere Titan got equal amounts of light and heat from the Sun, the northern polar hood shrank. Cloud activity continued for a while, until the passing of a large storm in 2010. Then, cloud activity dropped quite a bit. In the approach to northern hemisphere summer (southern hemisphere winter), the northern hood nearly disappeared, and now that we’re starting to see northern summer and southern winter. This latest discovery of clouds above a northern hemisphere ocean could signal summer weather patterns. Their appearance also leads the science team to speculate about whether (or how) the clouds are rela ted in some way to the seas. It’s possible that clouds form over the seas as a matter of course, but it’s also possible that Cassini just happened to catch some clouds racing over the ocean surface as part of a larger-scale circulation pattern.

Cassini will continue studying atmospheric change at Titan during the upcoming northern hemisphere summer (southern hemisphere winter). Already it has given us a great deal of information about the only other world in the solar system (besides earth) that has a fully developed atmosphere (and could possibly be habitable to certain forms of life). Stay tuned!

cassini, cassini mission, enceladus, saturn, titan

A Mini Nile on Titan

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Cassini’s Latest Find on Titan

A river and delta system on the surface of Saturn’s largest moon, Titan. Courtesy NASA/ESA.

The hits just keep on coming for the Cassini Solstice mission (a joint effort between NASA and the European Space Agency). This time it has sent back a radar image of what looks like a miniature version of Earth’s Nile River delta. It stretches across more than 400 kilometers (about 250 miles). Some kind of liquid is flowing through it, and scientists suspect that it is following along the boundary of a fault (a crack) in the surface. The river empties out into a Titan sea.

Titan is an interesting place. It’s got liquid flowing across its frigid surface, as well as lakes and small seas. Planetary scientists think the liquid that cycles from surface to the atmosphere and back again contains hydrocarbons such as ethane and methane. That’s not all that weird, really. Early Earth may have had a similar environment before things settled out some 4 billion years ago. What this image, and the many other images and observations about Titan tell us is that this is a lively world — it has activity on its surface, and there’s clearly something going on inside this moon that keeps things bubbling along. It experiences seasons, something that astronomers had not expected to find when they sent the mission.

The Cassini Solstice Mission is one of the great success stories in planetary exploration. It was launched as Cassini-Huygens in 1997 and has been tracing an orbital mission through the Saturn system ever since its arrival in 2004. It finished its initial four-year-long mission in 2008 and has been extended twice to continue exploring Saturn, its moons, and rings. It dropped the Huygens lander to the surface of Titan and that gave us our first in situ look at this once-mysterious moon.

The current mission goes through September 2017 and was renamed Cassini Solstice because it will have observed one complete turn of the seasons by May 2017.  It arrived just after Saturn’s northern winter solstice, hence the name.

Cassini’s greatest hits include the discovery and continual study of jets fountaining away from the moon Enceladus. This tiny world has a deep ocean that is kept warm by tidal heating (created by a tug of war between the gravity of Saturn and its outer moons, with Enceladus caught in the middle). The material spraying out from Enceladus has traces of organic chemicals in it, which suggests that Enceladus could be a place where primitive life could form (or may have already).

Saturn itself continues to be a target for the mission. Planetary scientists hope to use mission data to get a clearer picture of the gas giant’s internal structure, and gather more information about its atmosphere.

Want to know more about Cassini and its explorations? The Cassini Solstice Mission has a marvelous Web site where you can find out about the spacecraft, the science, and see many gorgeous images of the Saturnian system. Check it out!